Lubricant



Pat'ented Sept. 14, 1943 UNITED STATES PATENT OFFICE LUBRICANT No Drawing. Original application January 5,

1937, Serial No. 119,158. Divided and this application November 14, 1941, Serial No. 419,084

Claims.

Thi invention relates to improvements in lubricants and has for a principal objectthe provision of a compounded hydrocarbon lubricatgntg oil of highly improved "oiliness characters ics.

Another object of the invention is to provide a lubricating oil having pronounced "non-sludging" characteristics.

Another object of the invention is to provide a lubricating oil of sufficiently high stability to prevent the formation of gummy and resinous oxidation and polymerization products.

Another object is to provide a novel and simplified method of preparing the desired com pounded lubricating oil.

Further objects will become apparent as the invention hereinafter becomes more fully disclosed.

Lubricating oils for use in engines, particularly internal combustion engines, must have certain properties which tend to assure long continued operation of the engines by providing complete lubrication of the parts thereof, especially the cylinders, pistons and piston rings which are subject to severe heat conditions.

The above is particularly true of lubricating oils'manufactured specifically for use in internal combustion engines of the Diesel type in which higher compression pressures and higher airfuel ratios are essential operating factors.

To maintain such high compression for efficiency reasons the piston rings must function perfectly without sticking under the concomitant heat conditions to whichthe piston and piston rings are subject.

Also the above facts are true when applied to any type of internal combustion engine other than the Diesel type, even though in the ordinary spark ignition type of engine operating under relatively lower compression pressures than the Diesel type, the operating temperature range of the pistons and piston rings of said spark ignition type may be higher than that of similar parts of the Diesel type.

This is particularly true of the high speed Diesel type of engine equipped with aluminum pistons on account of the better heat conductivity of aluminum when compared to iron. However, the object of the invention is to design a compounded lubricating oil which will show the desired stability towards oxidation and polymerization over a wide range of heat and pressure conditions in order to fit-into the service of any kind of internal combustion engine, as partially illustrated by,

(1) .Engines operating on spark ignition of compressed gaseous fuels (gas engines),

(2) Engines operating on spark ignition of vaporized liquid fuels (gasoline engines).

(3) Engines operating with compression ignition of atomized heavy liquid fuels (Diesel engines).

In all these services it is essential that the lubricant has good afiinity for metal surfaces, which is maintained at the conditions prevailing on those surfaces under a wide range of temperatures and pressures.

In order to more fully comprehend the scope of the invention, it should be understood that mineral oilssuitable for lubricating oils consists of a mixture of different series of hydrocarbons. Depending on the origin of the crude oil, such mixture may include the saturated, the unsaturated, and the aromatic series of hydrocarbons, which are thus above defined for the purposes of the invention and any boiling range of finished lubricating oil may include one or more of the above series.

Heretofore in refining lubricating crude oil, it has been considered advisable to so treat the oil that most of the unsaturates and aromatic hydrocarbons will be removed and leave only a body of substantially saturated hydrocarbons for use as a lubricating oil. However such saturated oils are not only deficient in film strength or oiliness, and adherence to metal surfaces, but upon exposure to air at high temperature and high pressures, oxidation occurs in the cylinders of an engine, whereby acidic compounds are formed which is considered the initial step in their deterioration as lubricating oils.

Such oxidation products are of a resinous, oil

insoluble, type which gather around the piston rings in the ring grooves and cause piston ring sticking and thus the ultimate seizure and scoring of the piston in the cylinder.

, Inasmuch as oxidation in general is largely a. function of temperature, there is a certain temperature range within which saturated hydrocarbons might function well as lubricating oil in internal combustion engines without deterioration, but outside of which oxidation will occur.

When the above deficiencies of saturated hydrocarbons as a lubricating oil are attempted to be remedied by the inclusion of unsaturated hydrocarbons the acidic compounds formed as stated by oxidation of the saturated hydrocarbons cause secondary condensation reactions with the unsaturated hydrocarbons and thus cause the formation of an oil insoluble sludge detrimental to the function of the oil body as a lubricating oil.

In order to obtain a lubricating oil combining freedom from piston ring sticking tendencies with non-siudging characteristics, this invention pro- Oleic sold vides for the addition of certain metal compounds to a lubricating oil which has been processed suiilciently to remove undesired hydrocarbons and impurities, although it should be understoodthat a body of completely saturated hydrocarbons may be treated as herein set forth. The processing of the basic oil may be by well known methods, such as by selective solvents like liquid ment.

In the removal of the undesirable constituents of the oil by the above mentioned methods it may be desirable to retain in the oil certain compounds of acidic nature, as originally present in raw lubricating oil distlllates. Reference is specifically made to the so-called naphthenic acids, which by proper application of the treating methods may be left in the refined lubricatingoil. This will be further illustrated in the following description of the process herein disclosed.

There are two methods by which the invention may be practiced. In the first method a raw lubricating oil distillate containing organic acids normally present in such oil, such as naphthenic acids, is treated in the usual manner preferably with a selective solventoi the type liquid sulphur dioxide, phenol, dichlorethylether, furfural, nitrobenzene, or the like to yield a rafllnate comprising substantially those hydrocarbons which have the desired characteristics of a lubricating oil. To such treated oil is added sufllcient metal oxide or hydroxide, preferably calcium oxide or hydroxide, to form a metal soap in the oil; such soap comprising about between 0.01% and 1.0% by weight of the oil. The oxides or hydroxides are preferably selected from the group of the alkaline earth and earth metals, namely, calcium, strontium, barium, magnesium, zinc, aluminum, chromium. Most preferred of those enumerated is calcium oxide or hydroxide, not only by reason of economy, but also particularly because the calcium soaps are most effective for the purpose of imparting resistance to oxidation and non-sludging characteristics to the oil, but the invention is not limited thereto. 4

Alternatively the conversion of the free organic acid to a metal soap, more specifically a calcium soap may be accomplished by adding instead of of the lubricating oilis insuflicient to provide a desired percentage of incorporated soap as above described, suflicient organic acids may be added to the oil prior toisaponiflcation to obtain the required soapcontent, or a desired pre-formed metal soap may be added to an oil lacking in organic acidity in the desired proportions.

Again, in the event that the treated lubricating oil is lacking in contained organic acids, such acids may be added in the form of fatty acids together with equivalent portions of metal base to form the metal soaps.

In general, the higher molecular weight fatty acids are to be preferred where their calcium soaps are to be used and the type fatty acid to be used may include saturatedor unsaturated,

hydroxy, or polybasic fatty acids, or mixtures of the same. Carboxylic acids derived from cyclic nuclei in general are not particularly suitable for our purposes, primarily on account of their very low solubility but also on account of the relative instability of their metal soaps;

However, aryl-substltuted fatty acids of the type CnHiln2(AI)COOH, resemble in their solubility'and stability the ordinary fatty acids and therefore may be used in form of their alkyline earth metal soaps.

As examples of different organic acids, which have been tried-,the following tabulation may be presented, showing the solubility characteristics, the stability of the compounded oil and the sludge inhibiting characteristics of each particular soap.

The sludging test was carried out by heating a 100 gram sample of the oil, containing 1% by weight of the particular soap, to 330 F., for- 24 hours in presence of a metallic catalyst, which contains all the metallic elements present in the oil circulation system of an internal combustion engine (iron, copper, lead) which are also known as accelerators for oxidation.

TABLE No. 1

Characteristics of compounded oil after heat test Solubili of soaps in Metal soap added to mineral lubricating oil miners oil at room temperatures Appearance cel Lovibond None Slight carbonaceous deposit 550 Calcium soaps of saturated acid: I

Melissic acid, OrnHwOzm Slight precipitate of soap 40 Montanic aci CzaHu z. do 45 Cerotic acid, C2bHfl L Trasie precipitate of soap 0 Lhgioceric acid, 014E4 0; Be

Calcium soaps of unsaturated acids Cis uO Elaidic acid 'CISHIIOL Linoleic acid, 01,13,201 Telfairic acid, CriHnOz Opaque Clear '110 Slight precipitate oi 90 Trace of soap.'. j 6O Linolenic acid, 010 10 Tenn: No. l-Continued Metal soap added to mineral lubricating oil Solubilit oi soaps in minera oil at room temperatures Characteristics of compounded oil after heat test Appearance cell Lovibond Calclum loops of saturated hudrozy aclda Mono-hydroxy stcaric acid, CiIHuOKOH) Moderate 1m Dl-hydroxy stearic acid CnHuO1(OH)| 130 'lri-hydroxy stearic acid, C sHuOz 0H)... 170 'letra-hydroxy stearic acid, CnHn ml.- 200 Hexa-hydroxy stcaric acid, 01115004011). 260

Calcium soaps of unsaturated hudrory acids Ricinoleic acid, C HuOAOII) High Gummy precipitate 200 Calcium soup; of chlorinated acid: Chlorinated stearic acid... Moderate Clear 200 Chlorinated oleic acid.. High ..do 150 Calcium soaps of cyclic acids Benzoic acid, CtH|COOH 500 Salicylic acid, CaH4(OH)COOH. 500 Oinnarnic acid, C|H CH:CHCOOH 550 Hydrocinnarnic acid CIHCH2CH1COOH. 550 Phthalic acid, c.rrl(coon), o Na htholc acid, C|aH1COOH 550 Ah ctic 501d, CnHzaCOQH 7O Naphthenlcacid (extracted from petroleum) 55 Soups of metals other than calcium Magnesium melissate 150 Magnesium stearate 130 Magnesium oleate 100 Magnesium ricinoleate. 250 Magnesium naphthenate. 120 Strontium oleate Strontium naphthcnate 80 Barium stearate 150 110 220 150 Slight precipitate of soap 350 Heavy precipitate A; 400 Ole 200 250 Zinc naphthenate. itate of ZnO 400 Chromium oleate Heavy precipitate of CrrOsfl 220 Chromium naphthenat ..Cl0 do 250 1 Up to 0.1% by weight.

U to 0.5% by weight.

I ore than 0.5% by weight. w

The color of the original oil before heating and the addition of the soap, was between 10 and 20 in a Lovibond cell. A darkening of the color is therefore indicated by through color substantially above 20.

In this mode of operation the formation of the soaps involves the formation of molecular equivalents of water by reaction. This water has to be removed from the system because it interferes with the homogeniety of the soap-oil mixture. To this end, during the formation or addition of the desired alkaline earth metal soap in the oil, the temperature should be maintained at or sufficiently above the boiling point of water orthe pressure reduced to drive the same out of the oil. On the other hand, if a preformed desired soap is added to an oil, both the oil and the soap should be substantially dehydrated before mixing.

Within the percentage range of 0.01% to 1.0% by weight or alkaline earth metal soap to oil, it is found that the solubility of most of the soaps in I the oil requiring stabilization is definitely limited and is'in the lower brackets of the above percentages. Such solubility varies inversely with the carbon-hydrogen ratio of the oil, or with the degree of saturation of the oil. In consequence, the solubility of the alkaline earth metal soaps may be sufllcient to retain, the soap ina certain 011' without precipitation up to a relatively high percentage while, on the other hand, certain other desired hydrocarbon ofls will precipitate out a portion of the stabilizing soaps desired to be retained.

As an instance of this, lubricating oils derived from asphalt. or naphthene base crudes, whether treated or untreated, have a higher solvency kaline earth metal soaps in a. lubricating oil regardless of the origin or degree of refinement of the oil.

An increase in the solubility of alkaline earth metal soap and permanency of its solution in an oil may be accomplished by subjecting the mixture during formation of the soap or after the addition thereof to a temperature of at least about 400 F., for a, period of time suflicient to drive off all water formed by the saponification. However, with this heat treatment of certain oils, undesirable darkening will occur, and therefore it is preferred to use an agent which has a dispersing and homogenizing effect on the soap at Tetrachlorethane.

lower temperature to'make the same completely and permanently soluble in the oil and further to effect dispersal in such fashion that the soap remains in the oil as a clear solution without precipitation of any character whatsoever over an indefinite period.

These dispersing agents comprise two classes, either of which are effective.

(a) Agents which are of a boiling range lower than that of the oil and which are removed from the oil after having exercised their dispersing function.

(b) Agents which are of a boiling range not necessarily lower than that of the oil which will remain in the oil to serve as homogenizers for the compounded oil.

Agents of class a are solvents of an organic nature other than hydrocarbons, which have suflicient solvency power for both the oil and the alkaline earth metal soap used, and which have a boiling range lower than the oil but higher than that of water. Such solvents of class a which are found to be effective, include various alcohols, ketones, esters, ethers. Examples of such compounds found suitable, are compiled in Table No. 2 (Dispersing agents).

TABLE No. 2

Group AD1spersmg agents Dispel-sing Material used action upon soap Poor. Fair. Good. Do. Poor. Do. Do. Do. Good. yl ether Poor. Methyl ether of ethylene glycol. Good. Methyl ether of diethylene glycol. Fair.

' Methyl phenyl ether Good.

Benzyl ether Do. Butyric acid. Poor. Laurie acid. Good. Naphthenic acid. Do. Amyl acetate Poor. Cellosolve acetate Do. Dimethyl phthalate Do. Butyl lactate Do. Diacetone Fair. Methyl propyl ketone Good Dioxane Chlorbenzene Petroleum naphtha. Coal tar distillate... Methyl naphthalene Tetrahydronaphthalene.

Of these listed the methyl ether of monoethylene glycol is particularly useful in the process. This solvent has a boiling point of 285 F., and is especially adaptable to be mixed with an organic soap'of calcium for permanent solution 'in hydrocarbon oil because of the solubility of the like, which prevents darkening of the 011, and the mixture may thereafter be heated to a temperature corresponding to the" boiling point of the solvent, in the presence of the inert gas, or a temperature sufficient to drive off all the solvent and all the water but insuflicient to distil the oil.

Experiments confirm the fact that the desired dispersing agents of the type Class A should exercise the double function of dehydrating the soap while being soluble in the oil and by the mechanics of these functions it may readily be seen that an anhydrous soap is easily dispersed throughout the anhydrous oil to stay in permanent solution therein.

In order to render the solution of soap in oil permanent, it is preferred to subject the mixture to a prolonged heat treatment after the solvent (and water) has been driven off. Ordinarily there is a tendency for some of the soap to form a precipitate if suddenly chilled, or re duced in temperature immediately after removal of the solvent and water, but upon dilution of the precipitated mixture with further oil the precipitate will disappear. However, if a relatively concentrated solution of oil and soap, such as may be made by dispersing the soap in a relatively small portion of oil, is freed of its solvent and water and a temperature of about F., and above is maintained on the mixture for a period of about 24 hours, a clear solution will result which will remain clear indefinitely.

In this respect, it is preferable to so mix the soap and solvent with a small portion of the hydrocarbon oil and to make a soap stock concentrate and then at a later period, when convenient, to distribute the same in larger amounts of oil to bring the percentage of soap in the final product within the stated limits. This will be better appreciated when it is known that the solubility of calcium oleatein a California motor Agents of ClassB, which may be called homogenizing agents, include such types of compounds as the esters or others, or ester-ethers of high molecular weight fatty acids such as oleic or stearic acid, of which methylether of ethylene glycol oleate, diglycol laurate, digylcol oleate, may be illustrative. Also the esters of mono or polyhydric alcohols, partially or fully esterified, such as derivatives of amyl alcohol, glycol or glycerol, of which butyl oleate and amyl stearate are illustrative. By this method it is possible to incorporate even higher percentages of alkaline earth soap into any type of lubricating oil, As an example, it is possible to make a solution of up to 30% by weight of calcium oleate in an S. A. E. 30 grade motor oil, which will stay permanently clear and fluid and which can be blended in with more mineral oil to give a permanent clear solution of any desired concentration between O'and 30%. Examples of various homogenizingagents used are illustrate in Group B of Table No. 2A.

-more specifically chlorinated diphenyl.

Theta-iota dichlorste'aric ocid Further agents of Class B include halogenated aromatic compounds such as chlorine substitution products of aromatic hydrocarbons and Also certain aliphatic halogen compounds may be used advantageously as stabilizing agents for the compounded oils, such as halogen substitution products of high molecular weight fatty acids, or their esters. As an example may be given the methylester of monochlorstearic acid.

It is interesting to know that the use of homogenizing agents as above described has an added beneficial effect upon the film strength and metal aflinity of the lubricating oil. This is particularly striking with the halogen containing ingredients.

As a special case of great interest we wish to emphasize the following, in which a metal soap, more specifically a calcium soap of a halogenated high molecular fatty acid is usedas an oxidation inhibitor. We have found that metal soaps of a great number of halogen substituted fatty acids are not only readily soluble in mineral oils, but also impart very pronounced oxidation inhibiting characteristics to those oils.

It appears that the presence of the halogen in the fatty acid radical takes care of the desirable solubility characteristics as well as the film strength characteristics of the added ingredient, while the fatty acid radical still has preserved its oxidation inhibiting quality.

Metal soaps of the following halogen substi- Iota-chlorstcaric acid l CHa(CHz) .('JH(CH1)sCOOH Nu-chlor-erucic acid Thetn-iota-dichloroleic acid.

In compounding mineral lubricating oils in the various manners described, the general physical characteristics such as gravity, flash, and'flre points, and viscosity, are not materially changed so that the desired stability features in these lubricating oils can be obtained without necessitating any changes in S. A. E. rating. The following table shows a. comparison between a straight mineral oil and a. compounded product made from the same oil by addition of a metal soap, using either dispersing agents or homogenizers, or by addition of metal soaps of chlorinated fatty acids.

TABLE No. 3

Comparison of straight mineral oil with oil compounded ,for stabilization In the above disclosure a number of preferred methods have been indicated for the manufacture of a compounded lubricant containing from relatively minute to large-quantities of desired soaps. It should, however, be understood that this invention is not limited to the above examples, and it is possible to also manufacture compounded lubricants by a combination of these steps, and particularly within certain ranges of solubility, by the manufacture of a soap dissolved in a dispersing or homogenizing agent and the utilization of this mixture in compounding the oil. The scope of the invention is more clearly defined by the following claims.

This application is a division of our copending application Serial Number 119,158, filed January 5, 1937.

We claim:

1. A lubricating oil for severe service internal combustion engines comprising a naphthenic bas'e mineral lubricating oil containing about 1% 'of an oil-soluble soap of abietic acid, the soap having the property of controlling ring sticking in heavy-duty internal combustion engines and free from the property of imparting'substantial viscosity increase to the base oil in the stated amount. 1

2. A lubricating oil according to claim 1 wherein the soap is a calcium soap.

3. A lubricating oil for internal combustion engines comprising naphthenic base mineral lubricating oil from a California. crude and an oil-soluble soap of abietic acid in quantity sufficient to lessen piston ring sticking but insufllcient to increase materially the original viscosity of the naphthenic base oil.

4. A lubricating oil for internal combustion engines comprising a California mineral lubricating oil and about 1% of an oil-soluble soap oi abietic acid, the soap being present in quantity to control ring sticking in. heavy-duty internal combustion engines and free from the characteristic of imparting substantial viscosity increase to the base oil in the indicated proportions.

5. A lubricating oil according to claim 4 wherein the soap contains chlorine. 

